Color reproduction system



Patented Nov'. i1, ,-19521 'rnnnneiwarannrnnu appiicnu: september ii,195o. salama-icute -i j September l2', '190 tems, and more particularlyto color television. Color television systems heretofore proposed aresubdivided in two categories, namely: `simulf -taneous systems andsequentional systems.

In simultaneous systems,.a plurality of carrier 'frequency channels areemployed and a plurality pf image signals. one for each color. aresimi'iltaneously transmitted over the respective channels. The coloredimages are projected siinultaon a plurality of screens and these screensare-superimposed with respect to the observer's -eine. by means of anoptic system.

In sequential systems, the different image com ponents are transmittedover a single channel sequentially and are received in sufficientlyrapid succession so that the images reproduced there- 'from create theillusion of a complete image inA color when superimposed.

. llelm- (Ci. 17e-5.4) 'j vMyi'l'iventioii relatestcoolor reproductions-'I their order of succession beinz'choomlniheit manner-.that a couple ofcolors giving a 'visiteresultant is followed by another couple of( .alsogiving 'a white resultant.

The two colored images tc'a couple of colors yielding 'white areinuieratio 1/2 moi-certo oceupyontheseenef Sequential Systems are alsoknown in which 20 pairwise assorted colored images are simultaneouslyprojected on the photocathode of onesingle camera by means of an opticanamorp ser system adapted to reduce the hei'glil'i ini? ages, in whichthese images are scanned simultal neousiy and the couples 'of differentcolors of A these images are transmitted sequentially.

My invention relates to improvements in color television sequentialsyst'i'ns.

nie object of 'me invention is io 'reducethe 3 nickering ot theresulting image At the equality 'of flickering, the invention maken it'possible to increase .the number of nionochro'mic components namely toobtain a more exact reproduction of.

tolors without increasing the frame frequency,

that is to say without increasingthe band wi used for televisiontransmission.

` In the sequential system most commonly used,

, cessiye analyses mentioned above. bq'veen the namely tricolor System.the frame frequency for interlaced scanning is 60 .times per second,.and

the 'successive analyses are the following onesg.

lst sixtieth of a second. blue image, even lines 2nd sixtieth of asecond, green image. odd lines 3rd sixtieth of a second, red image, evenlines '4th sixtieth of -a'second. blue image. odd lines '5th sixtieth ofa'second. green image. even lines `1 "6th sixtieth of a second.redimage, odd linea "'iiiuis the even andgodd lines are scanned in thethree colorsinfon'e tenth of a second. and

the colors succeed 'each other at'the rate of 20 stimuli per second.

According to the present' invention the four color components of a scenebeing televised are the camera tube the same height 'as a'iin'gle'i'mlne' i i I The invention win be better nan the detaileddescription 'which Iolldv'r'x I fnd ich is given 'with reference to thedrawings in which: t

Figure l represents an image to ine-televised chosen for a bettercomprehension of the leading idea of the inventiom' vFigure 2 representsanalytic aignalsplot'tedon time base of an image in trichromic system;

Figure 3 illustrates the Maxwells triangle 'ci colors; i

Figur'esa and 5 representtically i. device for practical embodiment ofthe Figure l represents a colored image to b'e re produced. It comprisesilve horizontal bandsi'll green, i2 red, I3 blue; lI/white and' Ahbl.Each band is separated from the folloring one by black bands I6. il. i8.I9. which rower than the former ones.

Consider for example 'a 'record of this Imze expianaiion or theprinciple of the inven'uan.

No distinction w'iii therefore be made. in me nrs: sixtiein of a secondand the third one, be-

tween the second and the fourth, between the;

third and the sixth. 'A complete trichromiciscahningoiineimagewmbeinus'carnecoutin'tt.

of a second. Assume that the trichr'omic llters have a mission curvecorresponding to the selected colors (green. red. blue) and thereforeabsorb tvro thirds of the incident white light.

ter .and the portion 4comprised between not al A second and '%oo`f asecond corresponds to the projected sequentially, pairwise, the colorsand 65 scanning through the blue filter. Duringtnenmi Figure 2represents the amplitude of the l signal plotted on'a time base.' Theportion cotn prlsed between 0 and to of ,a second corresponds to thescanning through the green nlter, the por- 4tion comprised between the360 dhd36', of 'a second corresponds to the scanning through the redfilsixtieth oi a Vtherein-1re comprises estimulus 2| representing theimage o! the green band through a green nlter, the null portion 22 reprerenting at the Sametime the black bands I5. I1 and I8 and of the re'dbmd 8 2 and blue band I3 scanned through the green illter. a stimulus25' representing the image ci the white band il. the null dip 25representing the inzage` ot the black band I 9. a stimulus 2irepresenting the image ol the band i5, and n null 2l representing theimage oi the black band 2l.

During the second sixtieth of a second. there i successively appears anull 2l. (green band II A scanned through vthe red filter. and the blackband I6), a stimulus 29. (red band I2) a null 30 (black band I1, blueband I3 scanned through the iilter and the black band I8), a stimulus II(white band Il scanned through the red 1- ter). a null dip 32 (blackband I9). sstimulus 33 on the other hand. which respectively give l(band IS scanned through the red inter). a null' 2o dip 34 (black hand20).

During .the third sixtieth o! a second, there successively appears anull l35 (green handl II and red band I2 scanned through the hlue nlter,and

black bands-IS and I1), a stimulus 36 (blue band g5 I3) a null dip 31(black band I8). a Stimulus 38 `(white band I4 scanned through the bluelter) a. null dip 39 blanlsfoand I9) a stimulus l0 (band I5 scannedthrough the blue lter), a null dip 4i (black band 20). Y

At the end of one twentleth'oi a second the white appears bycombinationof pulses 2B, 3|. 38 with an amplitude shown 'at 42.

For each band of color: green. red. blue. white, complex. a luminouspulse is perceived by the eye every 1,50 of a second, but for the nrstthree colors the intensity of this pulse is at most equal to ya oftheintensity of a white pulse. The maximum, of flicker is obtained forthe white. as the dicker frequency is the same for all the luminouspulses whilst the brightness is the greatest for the white. In order toeliminate the flicker for the white color with respect to one of thebasic colors green.

red or blue, it would be necessary to increase threefold the framefrequency.

Onthe other hand .the persistence of vvision is not the same for each ofthe elementary colors,

' "its maximum corresponding to the blue. and

therefore every displacement o! the eye with respect to the screen wouldbe accompanied by a very troublesome blue dash.

The substance of the invention is to choose four selective lters,pairwise associated in two couples. such that each of thetwo couplesgives the white, and to arrange for these couples of filters toperiodically succeed each other.

3 represents the Maxwell's chromatic diagram of the InternationalIllumination Commission as plotted on the axes suggested by Mr.

W.'D. Wright in The Measurement of Colours (Adam Hilger. Ltd., London,1946). 'The points A. B. C. D represent the character- 'istics' of 4thechosen n lters. The points representing the filters are. of course,located inside o! the curve S whicnrepresents theplace of the visible.be coupled together. because in this case the white 'would appear atthe end of the two analyses according to composition Kx very diiierentfrom the white. and it would become white only after Iour successiveanalyses. i. e. the two successive' couples would give at iirst K1. thenKa. and the combination ot K1 and K: would sive the white.

Referring to Figures l and 5. 50 represen the object to be televised. 5Iand 52 denote two alters of respective characteristics A and C (or B andD) iitted into a rotating disc 53, (Figure 5), 54

is a double prism. -is an optical device adapted to anamorphise, in aratio of two to height oi' the colored images A (or B) aec': D). Ananamorpho'ser apparatus is described in U. S. Patent No. 1,897,752,issued February it 1933 to Georges chretien." Under these conci:

tions two images 5l and E8 are obtained on the photocathcde 5B of thevideo pickup devi total height of which is that of a normal The doubleimage is lscanned in one sixtieth of n.

second. 5l being of A-color and 58 of C-color.

:and then. the disc -53 having mean by a half-revolution. the double-imafg more scanned in one sixtieth of a second 5l being or nemmanc 5sbeing of D-lor. Although the invention has been descred 'with referenceonly to television. its Scope. however, appears suiiicient from theabove descri tion to enable those skilled inthe azi to eppgy the same toother problems of color reproduction.

Y ghatlclaim is:

01: :envision transmitting a' para' prising a television pick-up tubehxzvingt;z screen, a color iilter disc including four light llltersarranged in two dissimilar sets of complementary colors. the two ltersofleaglose having respectively the shape of a h alf cir l s, half ringconcentric to said circle, acdnll:

prism adapted to focus the light rays coming from the scene to betelevised thro lters of one set onto a cylindrical otics fniw:

cylindrical optics for forming two side by side imagesqhaving balancedcomplementary colors muy compressed in the ratio two. along side. onperpen cular tol their common Yvon n nmasonn.

REFERENCES orrsn v The following references are of Y me 0f this patent:

7o x color A and C. on the one hand. and B and D,

Number Name A 1,122,455 wom De Date 1,607,593 o'Grady .'--.'Il Nuev i3141,897,752 chretien Feb' 14' 926 2,207,409 Newcomer Jui' s' l 332,429,849 Somers "oecyzs' 1940 2,465,652 Legler M' 1947 2,520,842 Jumetar' 29' 1949 Aug. 29, 1950 :1: :an nim',

